Flash apparatus has become widely used in various kinds of optical apparatus of which the operation requires flash light. Particularly, in the art of photography, artificial light is used to illuminate an object to be photographed. One form of artificial light which is now widely used is the so-called flash tube.
It is common practice in electric flash devices to obtain high intensity illumination for photographic purposes by discharging a charged capacitor through a gas-filled flash tube. A low voltage D.C. power source is generally employed together with suitable circuitry in order to obtain the relatively high D.C. voltage which is needed to charge the flash capacitor for each firing of the flash tube.
To perform the flash photographing efficiently, it is necessary to control flash light quantity of the flash tube, notwithstanding flash timing of the flash tube.
It can readily be understood that under ordinary circumstances when an electric flash device is being used, the flash device requires a flash light exposure control circuit for sensing the light from the flash tube in order to perform efficiently flash light control.
In a conventional flash device, a driving power is supplied from a main storage capacitor which is used to generate the flash light in the flash tube. Accordingly, it is very inconvenient to supply the driving power to the exposure control circuit, since the power source by the main storage capacitor is likely to be lack to actuate the exposure control circuit.
Further, in thus conventional electric flash device, there was a disadvantage that circuit construction is relatively complicated, since the device is constructed such that the voltage is applied from a main electric charge storing capacitor to a flash light control circuit during a flash tube flashes.